This invention relates to electrical storage heaters.
Such heaters comprise a heat store, electrical means for heating the heat store, an internal air passage extending through the heat store, flow control means for controlling the convective flow of air through the internal passage, and means for actuating the flow control means.
The electrical heating means is powered from an electrical supply source which is only powered at certain restricted periods over each 24 hour period e.g., only from midnight until 7 am, referred to as an off-peak supply period. A small amount of heat stored during the off-peak period is dissipated but, with an adequately insulated heat store, the bulk of the heat is given out during the remainder of the time, referred to as the on-peak period.
The rate at which the heat is to be given out is not necessarily uniform: the storage heater should have an appropriate capacity for the room to be heated, but the amount of heat received or lost by the room from other factors such as solar heating through a window or loss due to draughts from an open door may vary and the flow means enables the rate of heat output to be varied accordingly.
The flow control means in such storage heaters is commonly a damper which is moveable by actuating means to cover and uncover an opening which communicates with the internal passage.
In one known form of storage heater (described in European patent number 017476), the actuating means comprises a bimetallic strip which acts on the damper and which is in turn deflected by a bellows communicating with a bulb sensor containing expansible liquid and sensing ambient temperature variations. The bulb sensor is responsible for causing the damper to open if the temperature in the room containing the heater drops unduly towards the end of an on-peak period, e.g., in the evening, in order to boost the heater output. The bimetallic strip is provided to assist closure of the damper at the start of an off-peak period, both because it is wasteful to heat the store with the damper open (the damper may well be open at the end of the on-peak period), and because it is dangerous so to do since the casing would become unduly hot. The bimetallic strip is positioned so that it is heated by the air rising from the internal passage when the heating elements inside the store are energised.
Nevertheless, it has been found to be desirable to include as well a pilot heater adjacent the room-temperature-sensing bulb sensor, operated by the off-peak electricity, in order to heat the bulb to assist the bimetallic strip in closing the damper. Alternatively the pilot heater may be positioned so as to heat the bimetallic strip.